Both professionals and volunteers. I have been burned on the air many, many, many, many times by firefighters and paramedics who didn't tell me they were on scene, didn't tell me they were transporting and didn't tell me they were at the hospital. I could play back the tape and prove it to them. But they would come up on the radio and say something like "Dispatch, I was on scene at 1800, transporting at 1815 and at the hospital at 1825. You acknowledged me. Please correct this." Bull crap. I could play back the tape at those times and there was no traffic from them. After a while you get sick of the general rudeness. If you don't know how to use your radio or you choose not to, don't blame me. I have had firefighters key up on the air and say stuff like "I'm enroute to 1234 main street and have been for 5 minutes." I would tell them that I already showed them enroute and they would say something like "Well, that's not what it says on my computer. Fix it." I'm sorry, but I can't fix their computers over the radio. I'm really not that good.
To be perfectly fair, police officers were not much better.